Drive fittings for pipe or conduit



Oct. 24, 1961 D. M. PHILLIPS DRIVE FITTINGS FOR PIPE OR CONDUIT OriginalFiled May 18, 1956 INVENTOR. DAVIS M.PHILL|P$ ATTORNEY United StatesPatent 25,062 DRIVE FITTINGS FOR PIPE 0R CONDUIT Davh M. Phillips, SouthMilwaukee, Wis., assignor to McGraw-Edison Company, a corporation ofDelaware Orldnal No. 2,966,372, dated Dec. 27, 1960, Ser. No.

585,727, May 18, 1956. Application for reissue June 1,

t 1961, Ser. No. 110,313

2 Claims. (Cl. 285-39) Matter enclosed in hasvy brackets appears in theorlglnal patent but forms no part of this reissue specification; matterprinted in italics indicates the additions made by reissue.

The present invention relates to fittings for frictionally joining pipeor conduit, and particularly relates to curvate fittings such as angularbends, elbows, and the like. The fittings disclosed hereinbelow haveparticular application for use with impregnated fibrous tubes, althoughequal benefit is obtained with any construction requiring sliding orslip-fit friction engagement.

It is now common practice to provide tubular housing for subterraneanelectric-wiring systems, such as electric power or telephone cables inwaterproof fiber conduit, and also to provide impregnated fiber pipe forvarious plumbing uses including sewer, drain, septic sewage systems andnumerous industrial non-pressure uses. The pipe or conduit sections usedfor such purposes are generally made by convoluting a wet web ofpapermaking pulp, as the web is being formed on a mandrel, into a tubeof the desired wall thickness. The tube is then dried and impregnatedwith molten pitch or bituminous compound.

It has become general practice to join links of conduit or pipe by meansof fittings that are driven in place in an axial direction tofrictionally engage the tubular memher by means of complementary taperedportions. The heat of driving tends to melt the impregnant to make afriction-welded joint.

There is little or no problem involved in driving a straight couplingfitting axially of said tube, as the fitting may be hit squarely at theend opposite from the tube along the axis thereof. However, in the caseof fittings requiring a bend such as a 45 or 90 fitting, it isdifficult, if not impossible, to strike the member with a direct blow.Consequently, there is a considerable tendency for the member to rake orcock relative to the longitudinal axis of the tube and consequentlyprovide a relative insecure joint, which is not desirable from awaterproof and rootproof standpoint.

It is therefore an object of the present invention to provide a drivefitting for frictional engagement with a tubular member, wherein saidfitting is curved or otherwise has an end deviating from the axialdirection of the tube.

It is a further object of the present invention to provide drivingbosses externally of said fitting, which bosses are positioned inpredetermined relationship to the axis common to both the fitting andthe tube to be joined therewith.

It is specifically an object of the present invention to provide adriving boss for a fitting frictionally engageable with a conduit orpipe, wherein the pounding surface of said boss is substantially normalto a line passing through the center of the interference cone of thetapered opening engageable with the member to be joined.

Fittings embodying features of the present invention are illustrated inthe accompanying drawings forming a part of this application in which:

FIG. 1 is a side elevational view of a 45 elbow fitting fabricated inaccordance with the present invention and shown fully engaging onetubular section, and with a portion cut away to show relative engagementwith another tubular member just prior to being driven to completefrictional engagement therewith.

FIG. 2 is a side elevational view of the elbow fitting embodying thepresent invention; and

FIG. 3 is a perspective view showing an elbow type fitting embodying thepresent invention in the process of being driven in place relative to ajoining complementary member.

Referring now to FIG. 1, the present invention is best described inconnection with a relatively short radius curvate fitting for joiningtwo sections of tubing, such as a 45 elbow, denoted in general by thereference numeral 1. As shown, the fitting 1 is in partial engagementwith a tubular pipe member 2. In the present case the pipe member isprovided with a male tapered conical portion 3, extending from one endthereof. A complementary internally tapered surface 4 is provided at oneend of the fitting 1 for frictional engagement with the outer surface ofthe portion 3. It is preferred that the angle of taper in both the maleand female portions be the same, for instance, 2, measured from thelongitudinal axis. However, it is to be noted that the relative lengthsof the mating members measured on the longitudinal axis are different,the axial length of the male frusto-conical portion being of slightlylesser dimension than the axial length of the female portion, forpurposes hereinafter described.

It will be seen that the complementary tapered portions 3 and 4 willinterfere with one another at some point determined by their relativeaxial lengths. The relationship between axial dimensions is readilyestablished by truncating the tapered end of the male portion 3 toprovide the end with a relatively larger diameter than the diameter ofthe internal taper 4 measured from the same axial points. Thus, apredetermined drive distance 5 is provided between the shoulder 6 on themember 2 and the extremity 7 of the fitting 1. This drive distance isdetermined by an interference cone of an axial length I, measured fromthe shoulder 6 to the internal shoulder 8 of the fitting 1. Thus, thetwo members 1 and 2 are' in freely slidable engagement with one anotherfor the major axial distance, the limit of which is established by thedrive distance 5. Beyond this point, the members must be driven togetherto provide a tight frictional engagement with one another. In the caseof pitch or bituminous impregnated member, the driving forces generateenough heat to melt the impregnant and thus provide an additionalsealing means between the members.

The present invention contemplates the use of specially positioneddriving bosses, such as the external bosses 10 and 11, which includepounding surfaces, or driving faces 12 and 13, respectively. Although,it is recognized that such bosses have been provided heretofore, it doesnot appear that any particular thought has been given to the relativeposition of the driving face on the respective embossment forestablishing a resultant force that will practically eliminate anytendency to cock or rake by one member relative to the other duringdriving operations.

I have found that by maintaining the plane of the respective drivingface substantially normal to a line lying in the plane of thelongitudinal axis of the curved tubular fitting and intersecting boththe center C of the interference cone (the axial length of which isdenoted by the reference character I) and the driving face, the fittingwill have practically no tendency to rake or cock relative to the member2 during pounding operations. As shown in FIG. 1, the driving face 13 ofthe embossment 11 may be maintained at any point on the outer arcuatesurface of the fitting 1 as long as it is substantially normal to theresultant force line 15.

It will also be observed from reference to the embossment 10, that theboss may be placed in various posilions on the outer periphery of thefitting, and preferably at a position of greatest radial length from thecenter C of the interference cone. Obviously, if it were possible, the.ideal position of the driving face 12 would be. in a plane normal to thelongitudinal axis 16 passing through the point C, which. axis would alsocoincide with the line of resultant force. However, practicalities ofdesign and manufacture generally limit the position of the embossment tothe position shown adjacent the inner end of the. radially extending hubportion 20.. As far as the embossment 11 is concerned, its position islimited to being adjacent the shoulder 21 abutting the tapered maleportion 22 of the fitting, which is frictionally engageable with thefemale taper of the member 25 (shown in FIG. 1 by the dot-dash lines),in the same manner as previously described in connection with thetubular member 2. In the latter case the center of the interference coneis denoted by the reference characer C. In addition, the member 25 isshown in full driven position relative to the fitting 1 to establishsealed frictional contact therewith.

With reference to FIG. 2, there is shown a preferred arrangement of theembossments 30 and 31 with respect to a conventional 90 elbow fitting32. In this connection, the driving faces 33 and 34 each lie in a planesub stantially normal to the longitudinal axes 35 and 36, respectively.

As previously described in connection. with FIG. 1, the fitting 32 isshown in interference position relative to a tubular member 40 (shown indot-dash lines) having a male. tapered conical portion 41 in positionjust prior to.

drive fitting. Thus, hammer blows, to a wood block applied, to thesurface 33 will complete the. drive to a sealed frictional engagementwith the member 40. The relative final positions are indicated inconnection with the member 45 (shown in dot-dash lines) in engagementwith the male tapered conical portion 4.6 on the fitting 32. The 90fitting readily lends itself to provision of the. driving faces 33 and34 in respective planes normal to the longitudinal axis for a directdrive along that axis.

In FIG. 3, a fitting, such. as the 45 fitting shown in FIG. 1, is shownin position for driving to complete the frictional engagement betweenthe members 2 and the fitting '1. It is preferred to put a block of wood50 or some other flat member for receiving the. direct blows from thehammer 51.

It will be apparent that they present invention has provided a drivefitting for conduit or pipe installations, which fitting is providedwith driving lugs or embossments in predetermined position with drivingsurfaces lying in preferred planes to substantially eliminate anytendency for raking or cocking between frictionally ell-- gageablemembers. during driving operations.

I claim:

1. A drive fitting assembly comprising afirst tubular, impregnated fibermember and a second curvate tubular [impregnated fiber] fitting memberaxially slidable into frictional engagement with said first member, oneof said members having an outwardly faced tapered fitting surfaceextending therefrom and the other member including an inwardly facedtapered surface complementary to and in engagement. with said firsttapered surface, said, engaged tapered surfaces before driving defininga cone of interference extending between the outer ends respectively ofthe engaged tapered surfaces, stop means to limit the relative movementof said surfaces as they are driven into tighter engagement whereby toprovide a predetermined axial driving distance, and means wherebydriving forces exerted on said curvate member act in a direction tounite said members with a minimum tendency for relative cocking andraking, making the joint substantially waterproof and root-proof, saidmeans comprising an impact driving boss integral with and positioned onthe longest radius external surface of said curvate member, said bosshaving a flat driving surface presenting a small area relative to thediameter of said members, said driving surface. being substantiallynormal to a line lying in the. plane containing the longitudinal axis ofsaid curvate member and intersecting both the center point of said coneof interference and said driving surface at substantially the centerthereof, so that the resultant line of force of any blow applied to saiddriving surface coincides with said line passing through said centerpoint of said cone of interference.

2. A drive fitting assembly comprising a pair of tubular impregnatedfiber members and a third curvate tubular [impregnated fiber] fittingmember, each of said pair of members having an end portion and saidcurvate member having two end portions each of which is coupled inaxially slidable frictional engagement with the said end portion of oneof said pair of members, one of said members at each coupling having anoutwardly faced tapered fitting surface extending therefrom and theother member including an inwardly faced tapered surface complementaryto and in engagement with said first tapered surface, said engagedtapered surfaces before driving defining a cone of interferenceextending between the outer ends respectively of the engaged taperedsurfaces, stop means to limit the relative movement of said surfaces asthey are driven into tighter engagement whereby to provide apredetermined axial driving distance, and means whereby driving forcesexerted on said curvate member act in a direction to unite said memberswith a minimum tendency for relative cocking and raking, making the jint substantially waterproof and rootproof, said means comprising a pairof impact driving bosses integral with and positioned on the longestradius external surface of said curvate member, each ,ofsaid bosseshaving a flat driving surface presenting a small area relative to thediameter of said tubular members, said driving surface beingsubstantially normal to a line lying in the plane containing thelongitudinal axis of said curvate member and intersecting both thecenter point of a cone of interference and said driving surface atsubstantially the center thereof so that the resultant line of force ofany blow applied to said driving surface coincides with said linepassing .through said center point of said cone of interference.

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